The Kanto region is expected to experience its first extremely hot day of 2026 today, July 22, with temperatures climbing sharply [1].

This surge in heat poses significant public health risks, prompting authorities to issue widespread warnings to prevent heat-stroke as the region faces unstable atmospheric conditions.

Central Tokyo reached 35°C around 9:30 a.m. [1]. By 11 a.m., more than 100 locations were classified as "moshobi," or extremely hot days [1]. Forecasters expect temperatures to peak at 40°C in Kumagaya and Nagoya [1].

Local authorities have issued heat-stroke alerts for 41 prefectures nationwide [1]. The Japan Meteorological Agency said the spike is due to a strong high-pressure system that is delivering intense sunshine across the region [1].

Officials said the heat is creating atmospheric instability. This environment can trigger sudden thunderstorms and strong gusts of wind, adding a layer of weather volatility to the high temperatures [1].

This heatwave follows a trend of rising temperatures throughout the summer. In some Kanto locations, maximum temperatures exceeded 33°C as early as June 1 [8]. Later, on July 13, parts of the Kanto-Hokkaido region saw temperatures above 25°C [9].

While some yearly projections from tenki.jp suggested only six to 10 locations nationwide would reach 40°C in 2026 [6], current data shows a more aggressive heat pattern. Previous reports from early September 2026 indicated over 200 locations had already been classified as "moshobi" [7].

“Central Tokyo reached 35°C around 9:30 a.m.”

The arrival of the first 'kokushobi' in Kanto, combined with temperatures hitting 40°C in cities like Kumagaya and Nagoya, signals an intensifying summer heat pattern. The issuance of alerts across 41 prefectures underscores the systemic risk of heat-related illness across Japan, while the potential for sudden thunderstorms suggests that high-pressure systems are creating volatile weather shifts that complicate urban disaster management.